KR100757734B1 - Apparatus and method for post video image process - Google Patents

Abstract

A video post-processing device and a method therefor are provided to have a narrow bus bandwidth. A deblocking filter(220) removes an artifact of a picture decoded by a video decoder(210). A differential picture encoder(260) generates a compressed differential picture on the basis of the picture filtered by the deblocking filter(220) and the decoded picture. A differential picture decoder(270) re-generates the filtered picture on the basis of the decoded picture and the compressed differential picture. The deblocking filter(220) removes a block artifact of the decoded picture.

Description

Apparatus and method for post video image process

1 is a view showing an imaging system including a conventional video post-processing device.

2 is a diagram illustrating an imaging system including a video post-processing apparatus according to an embodiment of the present invention.

3 is a diagram illustrating a differential picture encoder according to an embodiment of the present invention.

4 is a diagram illustrating a differential picture encoder according to another embodiment of the present invention.

5 is a diagram illustrating a differential picture decoder according to an embodiment of the present invention.

6 is a diagram illustrating an imaging system including a video post-processing device according to another embodiment of the present invention.

The present invention relates to a video imaging system, and more particularly, to an apparatus and method for post-processing a video image for a video imaging system.

Moving Picture Expert Group (MPEG) video compression is applied to a variety of applications. Video images provided in digital television broadcasting are compressed and transmitted in MPEG-2 format, and video images provided in digital multimedia broadcasting (DMB) broadcasting are compressed and transmitted in H.264 format.

Currently used video encoders remove inter-picture redundancy by temporal models based on motion estimation and motion compensation, and intra-picture redundancy by spatial transform and quantization based on Discrete Cosine Transform (DCT). -picture redundancy) and statistical redundancy by entropy coding. The DCT is performed in blocks of 8 * 8 or 4 * 4 size, and the energy of the block is concentrated in the low frequency region by the DCT. The DCT transformed block is quantized, and part of the original video image is lost during the quantization process.

The video decoder operates in reverse order with the video encoder. That is, the video decoder performs entropy decoding, inverse quantization, and inverse disc cosine transform (IDCT) on the coded video image, and then reconstructs the video image based on motion compensation. Since DCT is performed in units of blocks, block artifacts may appear in the video image reconstructed by the video decoder. Also, ring artifacts may appear near the edges of the reconstructed video image.

The H.264 video encoder includes an in-loop filter to remove artifacts that may appear in the reconstructed video image and to increase the efficiency of video encoding. However, in-loop filtering requires a lot of computation, and H.264 video encoders do not always perform in-loop filtering. MPEG-2 video encoders also do not include in-loop filters. Thus, block artifacts and ring artifacts issues may still exist.

To solve this problem, the video decoder includes a post filter. The post processing filter reduces block artifacts and ring artifacts present in the picture reconstructed by the video decoder.

Pictures in MPEG2 may be divided into I pictures, P pictures, and B pictures. An I picture means a picture that is coded without reference to another picture, a P picture means a picture coded using an I picture or another P picture as a reference picture, and a B picture is coded using two reference pictures Means pictures. A picture coded without referring to another picture like an I picture may be called an intra-picture, and a picture coded with reference to another picture such as a P picture or a B picture may be referred to as an inter-picture.

When coding a picture or decoding a coded picture, a prediction picture is needed. A picture used to generate such a predictive frame is referred to as a reference picture. In the MPEG2 scheme, an I picture and a P picture may be a reference picture, but a B picture cannot be a reference picture.

1 shows a conventional imaging system including a video post-processing filter.

The imaging system includes a video decoder 110 for reconstructing pictures, a deblocking filter 120 for filtering reconstructed pictures, a display unit 130 for displaying filtered pictures, a memory 150 and a bus serving as a picture buffer. 140).

Video decoder 110 decodes the compressed video data to reconstruct I, P, and B pictures. In order to generate the necessary predictive frames in the decoding process of reconstructing the I, P and B pictures, the video decoder 110 receives the reference pictures (I and P pictures) from the memory 150. Video decoder 110 decodes the compressed video data using predictive frames. The video decoder 110 provides the deblocking filter 120 with the reconstructed I, P, and B pictures, and stores the I and P pictures in the memory 150 for the next decoding process.

The deblocking filter 120 filters the I, P, and B pictures, and stores the filtered pictures (I ', P', and B 'pictures) in the memory 150.

The display 130 receives the filtered pictures I ', P' and B 'pictures from the memory 150 and displays the filtered pictures I', P 'and B' pictures. .

In fact, a picture and a picture that filtered the picture are almost similar. Conventional imaging systems require large memory capacities because they store nearly all similar and filtered pictures in memory 150. In addition, the conventional imaging system transmits the pictures filtered by the deblocking filter 120 to the memory 150 as it is, so that the use of the bus 140 is not efficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus and method for post-processing a video image that requires less memory space.

Another object of the present invention is to provide an apparatus and method for processing a video image having a low bus bandwidth.

It is yet another object of the present invention to provide an imaging system with less memory space and bus bandwidth.

 However, the above objects are exemplary and the present invention is not limited thereto.

In order to achieve the above object, a video image post-processing apparatus according to an embodiment of the present invention includes a filter for removing artifacts of a picture decoded by a video decoder, a picture filtered by the filter, and the decoded picture. A differential picture encoder that generates a compressed differential picture based on the differential picture decoder; and a differential picture decoder that regenerates the filtered picture based on the decoded picture and the compressed differential picture. The filter may remove block artifacts of the decoded picture.

The differential picture encoder generates a differential picture by comparing a filtered picture with the decoded picture when a type determination unit determines the type of the filtered movie and the type of the filtered picture is an I picture or a P picture. And a differential picture generation unit and a compression unit for compressing the differential picture.

The compression unit may code the differential picture using a run length code (RLC) scheme and recode the differential picture coded using the RLC scheme using a variable length code (VLC) scheme.

The differential picture encoder may further include a filter controller for adjusting the filtering coefficient according to the bandwidth occupied when the differential picture is transmitted on the bus.

The differential picture decoder generates a differential picture by decompressing the compressed differential picture when the type determination unit determines the type of the compressed differential picture and the type of the compressed differential picture is an I picture or a P picture. And a decompressor for reproducing the filtered picture by adding the decoded picture and the differential picture.

The decompression unit may decode the compressed differential picture using a variable length decode (VLD) scheme, and decode the differential picture decoded using the VLD scheme using a run length decode (RLD) scheme.

In order to achieve the above object, a video image post-processing apparatus according to another embodiment of the present invention includes a filter for removing artifacts of a picture decoded by a video decoder, and a reference region included in the picture filtered by the filter. And a differential region encoder for generating a compressed differential region based on the reference region of the decoded picture corresponding to the reference region, and the filtered picture based on the corresponding reference region and the compressed differential region of the decoded picture. And a differential region decoder for regenerating the reference region included in the.

The difference region encoder may include a type determiner that determines the reference region and the non-reference region in the filtered picture, a difference region generator that generates a difference region by comparing the reference region with a corresponding region of the decoded picture; It may include a compression unit for compressing the difference region.

The difference region decoder may include a type determination unit that determines a type of the compressed differential region, a decompression unit that decompresses the compressed differential region to generate a differential region, a corresponding reference region of the decoded picture, and the The apparatus may include a reference region regeneration unit configured to regenerate the reference region included in the filtered picture by adding a difference region.

In order to achieve the above object, a video image post-processing method according to an embodiment of the present invention includes a filtering step of removing artifacts of a picture decoded by a video decoder, and based on the filtered picture and the decoded picture. Generating a compressed differential picture and regenerating the filtered picture based on the decoded picture and the compressed differential picture.

In the filtering step, block artifacts of the decoded picture may be removed.

The generating of the compressed differential picture may include determining the type of the filtered picture, and comparing the filtered picture with the decoded picture when the type of the filtered picture is an I picture or a P picture. Generating a picture and compressing the differential picture.

In the compressing step, the differential picture may be coded by a Run Length Code (RLC) scheme, and the differential picture coded by the RLC scheme may be recoded by a Variable Length Code (VLC) scheme.

Generating the compressed differential picture may further include adjusting a filtering coefficient according to a bandwidth occupied when the differential picture is transmitted on a bus.

Regenerating the filtered picture may include determining a type of the compressed differential picture, and decompressing the compressed differential picture when the type of the compressed differential picture is an I picture or a P picture. And generating the filtered picture by adding the decoded picture and the difference picture.

In the generating of the differential picture, the compressed differential picture may be decoded by a variable length decode (VLD) scheme, and the differential picture decoded by a VLD scheme may be decoded again by a run length decode (RLD) scheme.

In order to achieve the above object, an image system according to an embodiment of the present invention includes a video decoder for decoding a video coded picture to reconstruct a reference picture to be used in a decoding process and a non-reference picture not to be used in a decoding process; A filter for removing artifacts of the reference picture and the non-reference picture, a differential picture encoder for generating a compressed differential picture based on the reference picture and the reference picture filtered by the filter, the reference picture and the filter A memory for storing the filtered non-reference picture and the compressed differential picture, a differential picture decoder for regenerating the filtered reference picture based on the compressed differential picture and the reference picture, and the filtered non-reference picture and the regeneration And a display unit to display the filtered filtered reference picture.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention.

2 is a diagram illustrating an imaging system including a video post-processing apparatus according to an embodiment of the present invention.

The imaging system includes a video decoder 210, a deblocking filter 220, a display 230, a bus 240, and a memory 250, like the conventional imaging system illustrated in FIG. 1. However, the imaging system further includes a differential picture encoder 260 and a differential picture decoder 270 to have less memory space and bus bandwidth.

Video decoder 210 decodes the compressed video data to reconstruct I, P, and B pictures. In order to generate the predictive frames necessary in the decoding process of reconstructing the I, P and B pictures, the video decoder 210 receives the reference pictures (I and P pictures) reconstructed in the previous decoding process from the memory 150. . Video decoder 210 decodes the compressed video data using predictive frames. The video decoder 210 provides the deblocking filter 220 with the reconstructed I, P, and B pictures, and stores the I and P pictures in the memory 250 for the next decoding process.

Deblocking filter 220 filters the I, P, and B pictures. The differential picture encoder 260 compresses the differential pictures I'-I for the filtered reference pictures I 'and P' pictures among the filtered pictures I 'and P' and B 'pictures. And P'-P pictures).

The compressed differential pictures (I'-I and P'-P pictures) and the filtered non-reference picture (B 'picture) are stored in the memory 250. Compressed differential pictures (I'-I and P'-P pictures) have a much smaller data size compared to filtered pictures (I 'and P' pictures). Accordingly, the memory 250 of the imaging system of FIG. 2 may be implemented as a memory having a smaller size than that of the memory 150 of the imaging system of FIG. 1.

Compressed differential pictures (I'-I and P'-P pictures) and reference pictures (I and P pictures) are provided to the differential picture decoder 270. The differential picture decoder 270 filters the reference pictures I 'and P' filtered using the compressed differential pictures I'-I and P'-P pictures and the reference pictures I and P pictures. Pictures) and regenerates the filtered reference pictures I 'and P' pictures to the display 230.

The display 230 displays the filtered reference pictures (I 'and P' pictures) and the filtered non-reference picture (B 'picture).

The deblocking filter 230, the differential picture encoder 260, and the differential picture decoder 270 perform a function of a video image post-processing device that removes artifacts of pictures reconstructed by the video decoder 210.

In this section, the bandwidth usage of the bus in the function of the video image post-processing device will be described. In the deblocking filter 120 of FIG. 1, the pictures I ', P', and B 'pictures that have been filtered by the display 130 are processed in the memory 150 through the bus 140. The filtered and filtered pictures I ', P', and B 'pictures are transferred from the memory 150 to the display unit 230 through the bus 140. In other words, when the imaging system of FIG. 1 post-processes pictures (I, P, and B pictures), the filtered pictures (I ', P', and B 'pictures) are written to memory 150. Occupies the bandwidth of the bus 140 when and when delivered to the display 130.

When the imaging system of FIG. 2 post-processes pictures (I, P, and B pictures), compressed differential pictures (I'-I and P'-P pictures) and filtered non-reference picture (B '). Picture) is transferred to the memory 250 via the bus 240, and filtered with reference pictures (I and P pictures) and compressed differential pictures (I'-I and P'-P pictures). The reference picture (B ′ picture) is transferred from the memory 250 to the differential picture decoder 270 via the bus 240. In other words, when the imaging system of FIG. 2 post-processes pictures (I, P, and B pictures), compressed non-pictures (I'-I and P'-P pictures) and filtered non-reference pictures. The B 'picture occupies the bandwidth of the bus 240 when it is written to the memory 250 and when passed to the differential picture decoder 270.

Since the I picture and the P picture have the same amount of data as the I 'picture and the P' picture, respectively, the condition that the image system of FIG. 2 occupies less bus bandwidth than that of the image system of FIG.

[Equation 1]

2 * Diff_PIC <PIC

Diff_PIC means the data amount of the compressed differential picture, and PIC means the data amount of the filtered reference picture. In general, the condition of Equation 1 is satisfied because the data amount of the compressed differential picture is much smaller than the data amount of the filtered reference picture.

3 is a diagram illustrating a differential picture encoder according to an embodiment of the present invention.

The differential picture encoder 260-1 receives the reconstructed pictures (I and P pictures) and filtered pictures (I ′, P ′, and B ′ pictures) by video decoding, and compresses the differential pictures. (I'-I and P'-P pictures) and filtered non-reference picture (B 'picture) are output.

To this end, the differential picture encoder 260-1 includes a type determiner 310, a difference picture generator 320, and a compressor 330.

When the filtered picture is input, the type determination unit 310 determines the type of the input picture. The differential picture generator 320 generates a differential picture by comparing the filtered picture with the reconstructed picture before filtering when the type of the input picture is an I picture or a P picture. The compression unit 330 compresses the differential picture in a lossless manner. In one embodiment, the compression unit 330 codes the differential picture by the Run Length Code (RLC) method, and recodes the differential picture coded by the RLC method by the Variable Length Code (VLC) method.

4 is a diagram illustrating a differential picture encoder according to another embodiment of the present invention.

The differential picture encoder 260-2 receives the reconstructed pictures (I and P pictures) and filtered pictures (I ′, P ′, and B ′ pictures) by video decoding, and compresses the differential pictures. (I'-I and P'-P pictures) and filtered non-reference picture (B 'picture) are output.

To this end, the differential picture encoder 260-2 includes a type determiner 410, a difference picture generator 420, and a compressor 430. The difference picture encoder 260-2 further includes a deblocking control unit 440 that controls the deblocking filter strength, unlike the difference picture encoder 260-1 of FIG. 3.

When the filtered picture is input, the type determination unit 410 determines the type of the input picture. The differential picture generator 420 generates a differential picture by comparing the filtered picture with the reconstructed picture before filtering when the input picture type is an I picture or a P picture. The compression unit 430 compresses the differential picture in a lossless manner. In one embodiment, the compression unit 430 codes the differential picture by the Run Length Code (RLC) method, and recodes the differential picture coded by the RLC method by the Variable Length Code (VLC) method.

The deblocking control unit 440 determines whether the bandwidth occupied by the differential picture (I'-I picture or P'-P picture) is smaller than the reference value. When the bandwidth is smaller than the reference value, the decompression control unit 430 determines that the differential picture (I) is smaller than the reference value. '-I picture or P'-P picture). When the bandwidth is greater than or equal to the reference value, the deblocking control unit 440 adjusts the deblocking coefficient for determining the deblocking filter strength. In other words, when the filtering strength is excessive and the bus bandwidth for the differential picture increases, the deblocking control unit 440 lowers the filtering strength to reduce the size of the differential picture.

The operations of the differential picture encoder of FIGS. 3 and 4 may be performed in units of blocks. In this case, the type determining unit determines whether the block belongs to any type of picture among an I picture, a P picture, and a B picture.

5 is a diagram illustrating a differential picture decoder according to an embodiment of the present invention.

The differential picture decoder 270 may reconstruct the pictures reconstructed by video decoding (I and P pictures), the compressed difference pictures (I'-I and P'-P pictures), and the filtered non-reference picture (B '). Picture) and output filtered pictures (I ', P' and B 'pictures).

To this end, the differential picture decoder 270 includes a type determiner 510, a decompressor 520, and a picture regenerator 530.

The type determination unit 510 determines the type of the compressed differential picture. The decompressor 520 decompresses the compressed differential picture when the type of the compressed differential picture is an I picture or a P picture to generate a differential picture. In one embodiment, the decompressor 520 decodes the differential picture compressed by the Variable Length Decode (VLD) method, and decodes the differential picture decoded by the VLD method using the Run Length Decode (RLD) method. Create The picture reconstructor 530 reconstructs the filtered picture by adding the reconstructed picture and the differential picture by video decoding.

The operation of the differential picture decoder 270 may be performed in units of blocks. In this case, the type determining unit determines whether the compressed differential block belongs to any type of picture among an I picture, a P picture, and a B picture.

In MPEG2, a B picture is not used when generating a predictive picture used when encoding or decoding another picture. In other words, in MPEG2, a B picture is a non-reference picture. That is, in the detailed description, I picture and P picture may refer to a reference picture that may be used when encoding or decoding another picture, and B picture may refer to a non-reference picture. However, when implementing the image system of FIG. 2 based on the H.264 video decoder, the I picture and the P picture described above may be replaced with the reference picture, and the B picture may be replaced with the non-reference picture. This is because, in H.264, a B picture may be a reference picture used to generate a predictive picture used when encoding or decoding another picture. Therefore, in the foregoing description, it should be interpreted that the I picture and the P picture mean a reference picture and the B picture mean a non-reference picture.

The video encoder is said to perform video coding by dividing the reference region and the non-reference region into one picture, and the picture reconstructed by the video decoder may be divided into the reference region and the non-reference region. The reference region may be divided into reference blocks, and the non-reference region may be divided into nonreference blocks. As described above, an image system when operated in a video decoding method including a reference block and a non-reference block will be described with reference to FIG. 6.

6 is a diagram illustrating an imaging system including a video post-processing device according to another embodiment of the present invention.

The imaging system includes a video decoder 610, a deblocking filter 620, a display unit 630, a bus 640, a memory 650, a differential block encoder 660, and a differential block decoder 670.

Video decoder 610 decodes the compressed video data to reconstruct the video coded blocks. The reconstructed blocks may be divided into reference blocks used in decoding other blocks and non-reference blocks not referenced in decoding other blocks.

The video decoder 610 receives the reference blocks reconstructed in the previous decoding process from the memory 150. Video decoder 610 decodes the compressed video data using reference blocks. The video decoder 610 provides the blocks reconstructed in the decoding process to the deblocking filter 620 and stores the reference blocks among the reconstructed blocks in the memory 650 for the next decoding process.

The deblocking filter 620 filters the reconstructed blocks. The differential block encoder 660 generates compressed differential blocks for reference blocks among the filtered blocks. Compressed differential blocks and filtered dereferenced blocks are stored in memory 650.

 Reference blocks stored in the memory 650, compressed differential blocks, and filtered dereferenced blocks are provided to the differential block decoder 670. The difference block decoder 670 regenerates the filtered reference blocks using the reference blocks and the compressed differential blocks, and the filtered reference blocks form a filtered picture together with the filtered non-reference blocks to display the display unit 630. Is provided.

The display 630 displays the filtered picture.

The video image post-processing apparatus according to the embodiment of the present invention requires less memory space and occupies less bus bandwidth. Accordingly, an imaging system including a video image post-processing apparatus according to an embodiment of the present invention may be implemented to include a small memory. The imaging system also has less bus bandwidth for image processing.

The above embodiments are all illustrative, and those skilled in the art may variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. And can be changed.

Claims (22)

A filter to remove artifacts of the picture decoded by the video decoder; A differential picture encoder for generating a compressed differential picture based on the picture filtered by the filter and the decoded picture; And And a differential picture decoder to regenerate the filtered picture based on the decoded picture and the compressed differential picture. The method of claim 1, And the filter removes block artifacts of the decoded picture. The method of claim 1, The difference picture encoder A type determination unit that determines a type of the filtered picture; A differential picture generator configured to generate a differential picture by comparing the filtered picture and the decoded picture when the type of the filtered picture is an I picture or a P picture; And And a compression unit for compressing the differential picture. The method of claim 3, The compression unit is a video image post-processing device, characterized in that for coding the differential picture by the Run Length Code (RLC) method. The method of claim 4, wherein And the compression unit re-codes the differential picture coded by the RLC method using a variable length code (VLC) method. The method of claim 3, wherein the differential picture encoder And a filter control unit for adjusting a filtering coefficient according to a bandwidth occupied by the difference picture when the difference picture is transmitted on a bus. The method of claim 1, The difference picture decoder A type determination unit that determines a type of the compressed differential picture; A decompression unit configured to decompress the compressed differential picture to generate a differential picture when the type of the compressed differential picture is an I picture or a P picture; And And a picture reproducing unit regenerating the filtered picture by adding the decoded picture and the differential picture. The method of claim 7, wherein And the decompressor decodes the compressed differential picture in a variable length decode (VLD) manner. The method of claim 8, And the decompressor re-decodes the differential picture decoded by the VLD scheme using a run length decode (RLD) scheme. A filter to remove artifacts of the picture decoded by the video decoder; A differential region encoder for generating a compressed differential region based on a reference region included in the picture filtered by the filter and a reference region of the decoded picture corresponding to the reference region; And And a difference region decoder for regenerating the reference region included in the filtered picture based on the corresponding reference region of the decoded picture and the compressed differential region. The method of claim 10, The difference domain encoder is A type determination unit determining the reference area and the non-reference area in the filtered picture; A difference region generator for generating a difference region by comparing the reference region with a corresponding region of the decoded picture; And And a compression unit for compressing the difference region. The method of claim 10, The difference region decoder A type determination unit that determines a type of the compressed difference region; A decompressor configured to decompress the compressed differential region to generate a differential region; And And a reference region regeneration unit configured to regenerate the reference region included in the filtered picture by adding a corresponding reference region and the difference region of the decoded picture. Filtering to remove artifacts of the picture decoded by the video decoder; Generating a compressed differential picture based on the filtered picture and the decoded picture; And And regenerating the filtered picture based on the decoded picture and the compressed differential picture. The method of claim 13, And the block artifacts of the decoded picture are removed in the filtering step. The method of claim 13, Generating the compressed differential picture Determining a type of the filtered picture; Generating a differential picture by comparing the filtered picture and the decoded picture when the type of the filtered picture is an I picture or a P picture; And And compressing the differential picture. The method of claim 15, And the difference picture is coded by a run length code (RLC) method in the compression step. The method of claim 16, The differential picture coded by the RLC method in the compression step is recoded by a variable length code (VLC) method. 16. The method of claim 15, wherein generating the difference picture And adjusting the filtering coefficients according to the bandwidth occupied when the differential picture is transmitted on the bus. The method of claim 13, Regenerating the filtered picture Determining a type of the compressed differential picture; Decompressing the compressed differential picture to generate a differential picture when the type of the compressed differential picture is an I picture or a P picture; And And regenerating the filtered picture by adding the decoded picture and the difference picture. The method of claim 19, And in the generating of the differential picture, the compressed differential picture is decoded by a variable length decode (VLD) method. The method of claim 20, The differential picture decoded by the VLD scheme in the step of generating the differential picture is decoded again by a Run Length Decode (RLD) scheme. A video decoder for decoding a video coded picture to reconstruct a reference picture to be used in the decoding process and a non-reference picture not to be used in the decoding process; A filter for removing artifacts of the reference picture and the non-reference picture; A differential picture encoder for generating a compressed differential picture based on the reference picture and the reference picture filtered by the filter; A memory for storing the reference picture, the non-reference picture filtered by the filter, and the compressed differential picture; A differential picture decoder that regenerates the filtered reference picture based on the compressed differential picture and the reference picture; And And a display configured to display the filtered non-reference picture and the regenerated filtered reference picture.

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